At present, network technologies have been developed, and the Ethernet technology thereof, with the characteristics of high openness, wide application, low cost and the like, has been gradually and widely applied to many fields, such as the information management and communication in the upper layer in the process control field and communication field of commercial computers.
In the distributed Ethernet, the clock synchronization technology is one of key technologies of the Ethernet technology, and the clock synchronization directly affects the real time property of the network communication. The IEEE1588 standard provides a solution for the clock synchronization in the Ethernet of which the basic function is making other clocks in the distributed network synchronous with the most precise clock. The IEEE1588 standard defines a Precision Time Protocol (PTP) which is used for performing submicrosecond synchronization of the clocks in sensors, executors and other terminal devices in a standard Ethernet or other distributed bus systems adopting multicast technology.
There are many switching nodes (such as switches and routers) inside a network, in the V2 version of the IEEE1588 protocol, it is required to calculate a residence time of related data in the switching nodes and a concept of transparent clock is proposed, i.e., subtracting the residence time of the 1588 protocol data in a switching node from the total transmission time of the data, so as to achieve the “transparent transmission” effect of the data in the switching node. Therefore, the time synchronization precision can be effectively improved by precisely calculating the residence time of the 1588 protocol data in the transparent clock (switching node) and by correcting the 1588 protocol data according to the residence time. Accordingly, in order to calculate the residence time of the protocol data in the switching node, the time information of the 1588 protocol data inputting into or outputting from the switching node must be acquired.
At present, in the related technologies, the IEEE1588 protocol stack is implemented and the related information of a time stamp (i.e., transparent clock) is acquired by software. Although the transparent clock of the 1588 protocol data can be implemented by software, there is still uncertainty and fluctuation, so that the synchronization precision can be seriously restricted due to the jittering of the software.
For the problems of poor precision, instability and strong fluctuation of the clock transparent transmission of the 1588 protocol data, there is still no effective solution.